Cartilaginous supporting plate below the adipose fin; small supramaxilla present in some genera; subocular shelf present; origin of anal fin under or short distance behind dorsal fin base; small photophores arranged in groups and rows on head and body (except in one species); scales usually cycloid (ctenoid in four species); swim bladder present (except in adults of a few species); vertebrae 28-45.
Myctophids are heavily consumed by numerous marine fishes and mammals. Most undergo a diurnal migration of several hundred meters. During the daytime the peak abundance of most species is between 300 and 1,200 m, while at night it is between 10 and 100 m.
About 32 genera with at least 240 species (Paxton et al., 1984; Paxton and Hulley, 1999; Zahuranec, 2000; Craddock and Hartel, 2003).
Subfamily Myctophinae. About 14 genera (e.g., Benthosema,, Centrobranchus, Diogenichthys, Electrona, Gonichthys, Hygophum, Myctophum, Protomyctophum, Symbolophorus, and Tarletonbeania).
Subfamily Lampanyctinae. About 18 genera (e.g., Bolinichthys, Ceratoscopelus, Diaphus, Gymnoscopelus, Lampadena, Lampanyctus, Nannobrachium, Notolychnus, Notoscopelus, Scopelopsis, Stenobrachius, and Triphoturus).
ACANTHOMORPHA (acanthomorphs)—spiny-rayed fishes. Rosen (1973a) recognized this taxon for all remaining teleosts, where many members throughout the taxon have true fin spines in the dorsal, anal, and pelvic fins. Stiassny (1986) and Johnson and Patterson (1993) gave further evidence of the mono-phyly of the acanthomorphs. The molecular studies of, for example, Wiley et al. (2000) and Miya et al. (2003) also supported acanthomorph monophyly. The molecular study of Chen et al. (2003) found several differences with what is presented here; interestingly, some of their results agree better with earlier morphological studies where the classification was based on overall similarity. Some of their results placed Gadiformes with zeioids; blennioids with Gobiesocoidei; Channoidei with Anabantoidei; Mastacembeloidei with Synbranchioidei and these two taxa grouping with Syngnathoidei + Dactylopteridae; Ammodytidae with Cheimarrhichthyidae; Zoarcoidei with Cottoidei; Percidae with
Notothenioidei; and a clade grouping many perciform groups and Pleuronectiformes. Their results, many of which agreed with that of other molecular studies, e.g., Wiley et al. (2000), Miya et al., 2003), and Smith and Wheeler (2004), will require detailed testing. Dettai and Lecointre (2005) also supported many of the above hypothesized clades and provided new hypotheses for certain acanthomorph clades. The next few years may see growing support for differing relationships than those presented here.
Johnson and Patterson (1993) presented arguments for regarding the lam-priforms as the primitive sister group to the remaining acanthomorphs. This is accepted here. In naming a higher monophyletic grouping, they introduced the new names Euacanthomorpha for the polymixiids and higher taxa and Holacanthopterygii for the Paracanthopterygians and higher taxa.
Patterson and Johnson (1995) presented a major study on the homologies of the intermuscular bones and ligaments of teleostean fishes. This study will not be reviewed here, but their conclusions must be considered in phyloge-netic studies of bony fishes. However, follow-up studies will be mentioned, dealing with acanthomorphs. In a wide selection of acanthomorph taxa, Gemballa and Britz (1998) tested Patterson and Johnson's (1995) hypothesis that the single bony series of intermusculars in higher acanthomorphs is the homologue of epineurals of lower teleosts. They concluded, in contrast to Patterson and Johnson, that the first intermuscular bone of Polymixia is an epicentral, the single series of intermuscular bones of Holacanthopterygii are epicentrals, and the neoneurals of some percomorphs are normal epineurals. In response, Johnson and Patterson (2001) argued that their identification of epineural ligaments above the intermuscular bones in many acanthomorphs is mistaken, that the structures in question are fanlike arrays of collagen fibers, not true intermuscular ligaments. Students of ichthyology should study these works as examples of how researchers can arrive at different conclusions. For related studies see also Chanet et al. (2004).
There is a rich fossil record of acanthomorphs (beginning in the Cretaceous). The Asineopidae is an acanthomorph fossil family of uncertain affinity. It contains one species, Asineops squamifrons of Eocene age from the Green River formation (Grande, 1984). It has a dorsal fin of 7-10 spines and 11 or 12 soft rays; the anal fin has two or three spines and 8-11 soft rays. Other fossil acanthomorph taxa of uncertain placement include the Blochiidae and Palaeorhynchidae (these two are often put with the Scombroidei), and the Cretaceous Aipichthyidae, Aipichthyoididae, Dinopterygiidae, Pharmacichthyidae, Pycnosteroididae, and Stichocentridae (e.g., Patterson, 1993). The first Cretaceous acanthomorph recorded from a freshwater deposit is Spinocaudichthys oumtkoutensis, described from the Cretaceous (Cenomanian) of Morocco (referenced in Filleul and Dutheil, 2004, and described by these authors in 2001). Wilson and Murray (1996) described Xenyllion zonensis (a paracanthopterygian placed in the family Sphenocephalidae), the oldest North American acanthomorph fossil and among the oldest anywhere, found in the Fish Scale Zone of the Albian/Cenomanian boundary (middle Cretaceous, about 99,000,000 years old). Stewart (1996) documented various fossil occurrences in North America, such as the sphenocephalid Neogastroplites from the middle Cretaceous, the polymixiid Omosoma and various holocentrids from the middle Late Cretraceous, and notes the Cretaceous diversity to be less than in other parts of the world.
Was this article helpful?